Why is the violin so hard to play?

I have never played violin, but I used to play guitar a lot at some point of my life, and still pick it up from time to time for a few nostalgic strums. Tunes from Violin I find moving if it played well and if the original tune has heart grabbing melody in its ups and downs sustenance and melancholic note. The article link included below treats playing guitar and violin in mathematical point of view that is a must read for interested ones who wouldn't mind a bit of mathematics and physics refresher.

Link:
Why is the violin so hard to play?